linux-kernel - Re: [PATCH 03/22] x86/kvm: Fix frame pointer usage in vmx

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Message-ID: <48ce6e66-6458-483a-f36b-9ea8e19cbc4e@redhat.com>
Date:   Mon, 15 Jul 2019 20:17:36 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Arnd Bergmann <arnd@...db.de>, Jann Horn <jannh@...gle.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH 03/22] x86/kvm: Fix frame pointer usage in vmx_vmenter()

On 15/07/19 15:35, Josh Poimboeuf wrote:
> On Mon, Jul 15, 2019 at 03:03:23PM +0200, Paolo Bonzini wrote:
>> On 15/07/19 14:37, Josh Poimboeuf wrote:
>>> Would it make sense to remove the call to vmx_vmenter() altogether, and
>>> just either embed it in __vmx_vcpu_run(), or jmp back and forth to it
>>> from __vmx_vcpu_run()?
>>
>> Unfortunately there's another use of it in nested_vmx_check_vmentry_hw.
> 
> Ah, I missed that too (failed by cscope).  Is this ok?

Yes, it is.  Thanks!

Paolo

> diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S
> index d4cb1945b2e3..4010d519eb8c 100644
> --- a/arch/x86/kvm/vmx/vmenter.S
> +++ b/arch/x86/kvm/vmx/vmenter.S
> @@ -54,9 +54,9 @@ ENTRY(vmx_vmenter)
>  	ret
>  
>  3:	cmpb $0, kvm_rebooting
> -	jne 4f
> -	call kvm_spurious_fault
> -4:	ret
> +	je 4f
> +	ret
> +4:	ud2
>  
>  	.pushsection .fixup, "ax"
>  5:	jmp 3b
>